Electric fuse



July 12, c LA M ELECTRIC FUSE Filed Sept. 12, 1929 INVE TOR W 1771a X AQENW,

Patented July 12, 1932 I UNITED STATES PATENT OFFICE FRANK 0. LA MAR, OF NEW YORK, Y ASSIGNOR TO GREAT WESTERN FUSE COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE ELECTRIC FUSE This invention relates to fuses, especially electric fuses of the enclosed type and more .particularly to fuses of this type in which there is a terminal projecting from each end of the fuse. g

It is Well known to those familiar with the fuse art that a fuse may be constructed by taking two terminals, preferably of the knife blade form, and connecting them by means of a fusible link. Such a device would well serve to interrupt an electric circuit in which it had been interposed when an overload or excessive flow of current occurred in such circuit. -When the fusible link is fused byan excessive flow of current the metal of the fusiblelinkis fused and melted and practically volatilized with the production of hot gas and flame. The hot metal is thrown and the flame plays on surrounding objects. In order to protect surrounding objects from injury by this hot metal and flame the fusi-' ble link may be surrounded by an enclosing body. Ordinarily, even when an enclosing body is used the heat and flame generated by the melting and combustion of the fusible link shoot out at each end of the surrounding body and have at least a potential ability for doing considerable damage to surrounding objects. The enclosing body cannot be sealed absolutely gas-tight because when the fusible link or element is fused by the excessive flow of current such a gaseous pressure is generated that the enclosing'body would be blown apart. It is necessary, therefore,'to provide some sort of a vent so that the gaseous pressure within the enclosing body may be relieved quickly enough to avoid a destructive action upon the bodyor case. To allow the hot gases or flame to issue from the enclosing body or case along the faces of the knife blade terminals is highly objectionable because they are thereby guided directly against the terminal clips in which the knife blades are placed. It is, therefore, desirable'to relieve the gaseous pressure generated Withinan enclosed'fuse by a method which will prevent the hot gases and flame from being guided directly toward any nearby surrounding object such as clips in which 6 the knife blade terminals are usually placed,

and to cool the gas before it issues to atmosphere.

A principal object of this invention is to provide a construction for a fuse of the type described in which the hot gases and flame generated by the fusing and combustion of a fusible link or element willbe allowed to gradually flow to the surrounding atmosphere along a path which will carr them alway from the nearby terminal or kni e blade 0 1 s.

-A further object of the invention is to so construct a fuse of the type described that directed through the gases and flame will be b a substantially elongated path or channel fore being allowed to flow to atmosphere.

A further object of the invention is to some-- what cool the gases before they are discharged into the atmosphere.

A further object of the invention is the construction of a fuse of the type described of such form that the hot molten metal caused by the fusing of a fusible element willnot solder the parts of the fuse together.

Further objects andadvantages will appear as the description of the particular physical embodiment selected to illustrate the invention progresses and the novel features of the invention will be particularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiment selected to illustrate theinvention reference is bad to the accompanying drawing in which like characters of reference designate corresponding parts throughout the several views, and in which:

Figure 1 is a plan view of a fuse embodying applicants invention with certain parts broken away and other parts separated to more clearly show the construction; Fig. 2, is an enlarged plan view of one end of the fuse as shown broken away to more clearly show the construction; Fig. 3, is anend view of the fuse, as shown by Fig. l, but with certain parts .removed to more clearly show the end construction and with dotted lines indicating a position of one of the parts during the process of assembly; Fig. 4, is an enlarged detail plan by Fig. 1 with certain parts view of one of the knife blade terminals and a closure washer together with a fragment of fusible link; Fig. 5, is a perspective View of a knife blade terminal with its associated flange as used in applicants invention; Fig. 6, is a separated view of a knife blade terminal and its associated flange as used in applicants invention; Fig. 7, is a fragmentary plan view of one end of the shell and end ferrule of a fuse embodying applicants invention.

For the purpose of explaining the principles and construction of my improvement in fuses I have illustrated the usual fusible link 1 in the drawing. This fusible link may be of the ordinary and well known forms. In accordance with usual custom the fusible link 1 is attached by means of the screw fastenings 2 to end terminals 3 and 4. These end terminals may be of any desired or appropriate form but are shown as of the knife blade type because peculiarly adapted for insertion in the ordinary and well known clips usually used in connection with fuses of the type to which my invention particularly relates.

The link 1 together with the terminals 3 and 4 constitute a complete fuse but for the reasons hereinbefore pointed out it is both desirable and necessary, because of the formation of hot gases and flame generated by the combustion of the fusible link 1 due to an overload or excess flow of current, to enclose the fusible link 1 so as to prevent injury to adjacent objects.

For the purpose of illustrating my improvement I have selected a well known form of surrounding body or cartridge 5. This cartridge 5 may be of any suitable or appropriate form but is preferably in the form of a hollow cylinder, as shown in the drawing, and is constructed of an insulating material, preferably, hard, dense fibre.

In order to provide a fastening for conveniently and properly closing the ends of the cylindrical body 5 I have illustrated the well known ferrules as 6 and 7 on each end of the body 5. These ferrules in practice, although not necessarily so, are identical in construction and for the purpose of explaining my improvement I prefer to illustrate these ferrules as being identical in construction although my specific improvement does not necessarily require that the opposite ends of the body 5 be provided with exactly identical construction.

As shown in the drawing, the ferrule, as 7, includes a portion, as more particularly shown in Fig. 2, which surrounds body 5 and is rigidly attached thereto in any approved and well known manner, as by forming an internal thread upon the ferrule and an external thread upon the body 5. In the drawing I have illustrated the ferrules attached as by rivets 8 passing through both the ferrule and the body. In the particular form of ferrule selected the outer end is provided with an external screw thread 9 formed on a slightly reduced portion of the ferrule. The thread 9 is stopped a little short of the shoulder 10 for a purpose to be hereinafter explained.

The ferrule, as 7, has an end face 11 and is formed with a web 12, best shown in Fig. 3. This web may be of any desired form but preferably includes faces forming an aperture 13. This aperture 13, in the particular form of construction shown, includes parallel side walls 14 and 15. By such construction of the web an aperture in the web of proper shape is formed for receiving a substantial square or rectangular body which when received within the aperture is prevented from turning.

In my construction a collar or flange 18 is received and fits within the aperture in the web 12 about midway the thickness of the flange, as best shown in Fig. 2.

By the construction of terminal 4 and flange 18 as hereinbefore described, and as is more particularly seen by reference to Fig. 4, the flange 18 will fit into the recess or aperture of the ferrule web 12 and the shoulders 23 and 24 of the terminal will bear against the face of the web 12. The collar 18 being retained on the terminal by the upsets 34 and 35 and fitting into the aperture in the web 12 will prevent the terminal from turning and the shoulders 23 and 24 will prevent the terminal from moving inwardly into the body 5.

In order to maintain the terminal 4 in the position as shown in Fig. 1 and to form a closure for the openings of the web 12 the slotted washer 25 is provided which as shown in Fig. 2 is provided with a. slot 26 which allows the terminal 4 to pass therethrough. The washer 25 when slipped over the terminal 4 and moved toward the end 19 thereof comes in contact with the collar or flange 18 as best shown in Fig. 2.

The cap 27 provided with an internal thread 28 is provided to cooperate with the external thread 9 on the ferrule 7. The cap 27 is provided with the flange 29 forming the opening 30. IVhen the cap 27 is slipped over the terminal 4, the threads 28 are brought in cooperation with the threads 9 and the cap through the flange 29 is brought to bear firmly against the interposed washer 25. The cap when screwed home is illustrated in Fig. 2 and at the left hand end of Fig. 1. In the position as thus shown the washer does not contact with the end face 11 of the ferrule 7. The washer contacts with the collar or flange 18 and so holds the terminal shoulders 23 and 24 firmly against the web 12 but this contact of the washer 25 against the flange 18 due to the position of shoulders 23 and 24 in relation to the outside face of the flange JUL? 18 prevents the inside face of the washer 25 from contacting the end face 11 of the ferrule 7 so that when assembled there is always the space 31 as best shown in Fig. 2 between the washer 25 and the end face 11 of the ferrule 7. In order to be certain that this space 31 always exists the washer 25 is made of such thickness that the cap 27 may not be screwed onto the ferrule 7 sufiiciently tightly to flex the washer 25 so as to bring it into contact with the end face 11 of the ferrule.

By reference, particularly, to Figs. 2, 3 and 7, it will be seen that transverse grooves 37, 38, 39 and have been formed in the thread 9. Applicant may form one or any number of these grooves in the thread 9. The number will depend entirely upon the quantity and rapidityof generation of gas within the shell 5, and the desired speed of liberation. The grooves may be of greater or less depth, or as shown by 37 and 39, may have the bottom slant upwardly and away from the end face 11 at a greater or less angle.

The parts assembled are well shown in Fig. 2. The washer 25 is caused to bear so firmly upon the flange 18 that gases or hot flame may escape only to an inappreciable extent at this point. The same is true of the contact between the washer 25 and the flange 29. In order for the gases generated within the body 5 by the fusing or combustion of the fusible link to escape they must flow into the space 31 and from thence through a groove, as 37, impinging against shoulders 10 or into the cooperating screw threads 9 and 28 and then by a free but tortuous path to the point 32, as shown in Fig. 2, where they escape to atmosphere as they impinge upon the shoulder 10 spaced somewhat from the end 33 of the cap 27 so as to afford an escaping point.

By properly proportioning the space 31, and the number, depth and bottom slant of the grooves, as 37, the internal pressure caused by the volatilization of a fuse link maybe relieved at any desired speed suitable to protect both the shell 5 and nearby objects.

In order to be certain that a proper path exists through the cooperating threads 9 and 28 applicant prefers to make the external diameter of the threaded portion 9 a slight amount under-size or the internal diameter of the threaded portion 28 slightly over-size. This construction provides at all times a free but tortuous passage for the escape of hot gas and flame from the interior of the body 5.

Applicant prefers a construction in which both ends of the body 5 are similarly constructed and arranged to the end that the terminals 3 and 4 and the link 1 together with flanges 18 may be assembled as a unit and then inserted endwise of the body 5 having the ferrules 6 and 7 in place thereon. In order to provide for this applicant forms the web 12 with a large cut-away portion 36, as best shown in Fig. 3, so that the terminal as 4 with the flange 18 thereon may be passed therethrough sufliciently to allow the terminal 4 to be moved sideways into position as shown in'Fig. 3. The dotted line position shows the position of the terminal 4 and flange 18 after it has been passed endwise through the ferrule 7 and body 5, but before it is moved sideways.

Although the grooves, as 37, and the spaced washer, as 25, have been shown in connection with a knife blade type, nevertheless, this is not to be understood as implying that they may not be used with a ferrule type fuse.

Although applicant has illustrated a preferred embodiment of his invention and described the construction and principle thereof, nevertheless, it is to be understood that the form selected is merely illustrative but does not exhaust the possible physical embodiment of means underlying, the invention.

What is claimed as new and is desired to secure by Letters Patent of the United States, 1s:

1. In an electric fuse; in combination: a hollow tubular body formed with an external helical groove adjacent an end thereof; a flanged cap formed with a mating internal helical groove; a washer interposed between the end of the body and the flange of the cap; means including a terminal blade for spacing the washer from the end of the body whereby a space is provided for the escape of gases and an empty groove transverse to the external helical groove formed therein communicating with said space at one end and with the atmosphere at the other end for the escape of gases to the atmosphere.

2. In an electric fuse, in combination: a hollow externally grooved body; a terminal projecting beyond the end of the body from the space within the body a washer positioned in front of the end of the body and means on the terminal spacing the washer from the end of the body whereby a space is provided for the escape of gas; means borne by the terminal for holding said washer in spaced position and an empty groove transverse to the external helical groove formed therein communicating with said space at one end and with the atmosphere at the other end for the escape of gases to the atmosphere.

3. In an electric fuse, of the enclosed refillable cartridge type the combination of a metallic ferrule formed with an external thread, said thread formed with an empty transverse groove for the escape of gases to the atmosphere and means for conducting gases generated within the cartridge to the groove.

4. In an end construction for an electric fuse, in combination: a hollow shell of insulating material; a metallic ferrule rigidly attached to the end of the shell, said ferrule formed with an external thread for a portion of its length and said thread formed with 10 atmosphere.

FRANK C. LA MAR. 

